The present invention relates to apparatus for controlling motors of a mechanism having several motors. More particularly, the present invention relates to apparatus for monitoring and controlling power supplied to motors of a mechanism, such as a robot, which has several motors.
Various mechanisms, such as robots, have several motors to power their operation. Hitherto such mechanisms, including robots, have been provided with a single power supply device common to all the motors of the mechanism. Servo-amplifiers have been located in a common switch cabinet which, due to its size and weight, is installed outside the mechanism work space. The servo-amplifiers are controlled with analog signals or field buses.
This is disadvantageous in that high cabling expenditure is involved. In addition, electromagnetic and line-linked disturbances or interference cannot be excluded and must be taken into consideration. High costs are also involved for cooling and safety assurance. The known power parts also have a high space requirement and are not flexible as regards handling or extension.
The problem addressed by the present invention is, consequently, to provide an apparatus for the control of power suppled to motors of a mechanism having several motors which apparatus, while avoiding the aforementioned disadvantages, requires only a very low expenditure, particularly with regards to cabling, and whose operation gives rise to minimum electromagnetic and line-linked interference and provides improved monitoring and control of the motors, while having high efficiency.
In accordance with the present invention, each motor of an installation having several motors is provided with its own driver unit, and the driver units are interconnected with each other and with a control unit by means of a series circuit or of a ring circuit. In one preferred embodiment, each driver unit is preferably provided with a memory device, such as a shift register, to store commands and/or data transmitted from and to the control unit. As a result of the subdivided design of the power supply through the use of individual driver units for each motor and the connection thereof with the control unit by means of a ring circuit or a series circuit, it is possible to position the individual driver units close to the mechanism, and in particular close to the individual motors associated therewith. This results in minimum cabling costs. Additionally, electromagnetic and line-linked interference are significantly reduced, because only limited interference is caused by the short motor lines. As a result of the subdivided arrangement of the driver units, the costs for cooling and assuring the necessary safety are kept low. The driver units have a limited space requirement, and the number of motors and driver units can be modified economically and in a flexible manner.
According to one preferred embodiment, the driver units are connectable directly to a voltage network by means of a mains line. As a result, power can be provided directly by the power line or mains voltage, so long as the mains voltage and the control unit voltage are compatible, such as is the case with a control unit voltage in 600 V technology with respect to the European three-phase 400V supply network. This reduces the power distribution costs, and the supply voltage can easily be handled, particularly switched and connected. A further advantage of the invention is that the dissipated heat can be removed in a passive manner, and consequently there is no need for active cooling elements such as fans or heat exchangers. According to a preferred development, the driver units have their own rectifiers and are consequently self-sufficient.
As a result of the interconnection of the driver units by means of a ring circuit or a series circuit, all the driver units are interlinked by a rapid, deterministic bus, which can be connected to the control unit by means of existing SSI interfaces. A repeater function is obtained, in which each driver unit automatically becomes a separation point or break, to which it is possible to connect a communication cable without any technical limitations, and consequently flexible extendability exists in the application. This also permits simple monitoring of the functioning of the individual driver units.
If a command or data is sent on the ring circuit or the series circuit, but a particular driver unit has failed, i.e. the control unit receives no reply after a given, critical time, or if the ring circuit or series circuit has a fault, the control unit recognizes that a fault exists and can stop the mechanism in an appropriate manner. Another advantage of the ring or series architecture according to the invention is that addressing of the driver units is possible by their position in the circuit, and consequently there can be a logic association by software, so that it is not necessary for the individual driver units to have specified addresses. However, if desired, each driver unit can have an address, with each transmission from the control unit including the address of the intended driver unit.
In the series architecture driver units are connected to each other and to the control unit by both an outgoing line and a return line. Thus, the control unit is connected to a first driver unit by means of an outgoing line and a return line, the first driver unit is connected with a second driver unit by an outgoing line and return line, and the second driver unit and further driver units are connected to their respective following driver units by respective outgoing lines and return lines.
In the ring architecture, the driver units are connected to each other and to the control unit in series by an outgoing line from the control unit, the return line going directly from the last driver unit in the ring back to the control unit. Thus, the control unit is connected to a first driver unit by means of an outgoing line, the first driver unit is connected with a second driver unit by an outgoing line, and the second driver unit and possibly further driver units are connected to their respective following driver units by respective outgoing lines. A return line from the last driver unit in the ring is connected directly back to the control unit.
According to a preferred embodiment, the ring circuit or the series circuit is formed by symmetrical pairs of wires or optical waveguides. Such a line has a high disturbance immunity, which is not the case with two parallel lines, because the latter cannot be twisted and symmetrized.
According to another preferred embodiment, each driver unit has its own signal processor. By means of the signal processor the driver unit communicates with the control unit, to which it is connected by the ring or series circuit. According to another preferred embodiment, monitoring units for monitoring pick-ups are integrated into the driver units.
In a further preferred embodiment, each driver unit includes a memory device, such as a shift register, which enables the driver unit to store commands and/or data received from or to be sent to the control unit. The commands or data can be positioned in the data flow in accordance with the position of the driver unit in the ring circuit or the series circuit so that no address is necessary for the driver unit. Alternatively, each driver unit can be identified by an unique address, and the commands or data can include the address of the particular driver unit to which or from which the commands or data are being transmitted. These approaches permit transmission of commands or data from the control unit to each driver unit and/or from each driver unit to the control unit.
As a result of the inventive construction of subdivided driver units advantageously connected by means of a ring circuit or a serial circuit, despite the low cost a high disturbance immunity is obtained. As a result of the ring or series structure of the circuit, there is no need for address configuration by the user. The possibility exists of communicating large data quantities over considerable distances, so that it is possible to remove the driver units from the control unit and operate the driver units as independent units. The ring circuit or series circuit also aids circuit efficiency, in that it is possible to interconnect any number of driver units. As stated, the driver units can be located directly at the drives of the mechanism, and yet even in subdivided systems of considerable size, short motor lines are possible. Thus, the mechanism configuration has no influence on the electromagnetic compatibility and the line-linked disturbances.
The present invention also provides a control circuit capable of efficiently exchanging messages between the control unit and each of the driver units so as to enhance the control.